The aspects of the invention relate to capacitor fabrication methods including forming insulative barrier layers and capacitor constructions having insulative barrier layers.
Capacitors are common devices used in electronics, such as integrated circuits, and particularly semiconductor-based technologies. Two common capacitor structures include metal-insulator-metal (MIM) capacitors and metal-insulator-semiconductor (MIS) capacitors. One important factor to consider when selecting a capacitor structure may be the capacitance per unit area. MIS capacitors may be advantageous since a first electrode as the semiconductor may be formed of hemispherical grain (HSG) polysilicon that exhibits a higher surface area in a given region compared to a planar surface of amorphous polysilicon. The higher surface area provides more capacitance per unit area occupied by a capacitor.
However, a high K factor (also known as dielectric constant or xe2x80x9cxcexaxe2x80x9d) dielectric material may be desirable to further enhance capacitance. Ta2O5 is one example of a high K factor dielectric, but it inherently forms an interfacial dielectric layer of SiO2 when formed on a capacitor electrode comprising HSG. The interfacial dielectric exhibits a lower K factor than Ta2O5 and thus reduces the effective dielectric constant for the capacitor construction. Such reduction may be significant enough to eliminate any gain in capacitance per unit area otherwise achieved by using HSG instead of a planar electrode. Use of other oxygen containing high K dielectric materials has proved to create similar problems.
Because it may be desirable to provide area enhancement of an electrode in a MIM structure using HSG, one attempt at addressing the stated problem is forming a silicon nitride insulative barrier layer over the HSG. The silicon nitride barrier layer may be formed by nitridizing the silicon of the outer surface of HSG. Unfortunately, silicon nitride exhibits a K factor of only about 7, less than the K factor of some high K factor dielectrics that are desirable. Accordingly, even the silicon nitride barrier layer reduces the effective dielectric constant of the capacitor.
In accordance with one aspect of the invention, a capacitor fabrication method may include forming a first capacitor electrode over a substrate and atomic layer depositing an insulative barrier layer to oxygen diffusion over the first electrode. The method may further include forming a capacitor dielectric layer over the first electrode and forming a second capacitor electrode over the dielectric layer. By way of example, the atomic layer deposited barrier layer may comprise Al2O3. Also, the barrier layer may exhibit a K factor of greater than about 7 at 20xc2x0 C. The dielectric layer may be over the barrier layer.
In another aspect of the invention, a capacitor fabrication method includes forming a first capacitor electrode over a substrate, chemisorbing a layer of a first precursor at least one monolayer thick over the first electrode, and chemisorbing a layer of a second precursor at least one monolayer thick on the first precursor layer. A chemisorption product of the first and second precursor layers may be comprised by a layer of an insulative barrier material. A capacitor dielectric layer may be formed over the first electrode and a second capacitor electrode may be formed over the dielectric layer. As an example, the first precursor may comprise H2O and the second precursor may comprise trimethyl aluminum. The dielectric layer may contact the barrier layer.
In yet another aspect of the invention, a capacitor fabrication method includes forming an opening in an insulative layer over a substrate and forming a layer of polysilicon in the opening. The polysilicon layer may be converted to a first capacitor electrode. An insulative barrier layer may be conformally formed on the first electrode and may comprise Al2O3. The barrier layer may be sufficiently thick and dense to reduce oxidation of the first electrode by oxygen diffusion from over the barrier layer. The method may further include forming a capacitor dielectric layer comprising oxygen on the barrier layer and forming a second capacitor electrode over the dielectric layer.
Other aspects of the invention include the capacitor constructions formed from the above described methods.